In that paper, Soto mentions that The Dictionary of Early English traces snark to snirt. snirt means
To laugh in a suppressed manner, to snicker. 18th and 19th centuries. In the same period, snirtle, to laugh even more quietly (but mockingly), to snigger. All these words are echoic; also sniff; snark; snork; snort; snur, to snort; snurt, to snore, to sneer, to snore. Snurt was first written in the 15th century; a snurter was a snorer...Also snite, to wipe the nose; snot, to blow the nose. Snot, also snat, nasal mucus was common (but not vulgar) from the 15th through the 17th century; earlier it meant the snuff of a candle, the burnt part of a candle wick.
Curious about The Dictionary of Early English, I had a look - it's freely available here. It was written by Joseph Twadell Shipley and published in 1955. It covers terms from the 8th to the 18th centuries that have fallen out of use. Check out the entry for snark!
snark. See snirt. But also, to find fault - a 19th century use. Beware of the Boojum!
Indeed. Anyway, we're dealing with two snarks here. The OED says:
snark v. dial. [Corresponds to MLG. and LG. snarken (NFris. snarke, Sw. and Norw. snarka), MHG. snarchen (G. scharchen †schnarken), of imitative origin: cf. SNORK v.]
1. intr. To snore; to snort
1866 N. & Q. 3rd Ser. X, 248/1 I will not quite compare it [a sound] to a certain kind of snarking or gnashing. 1907 Westm. Gaz. 9 Nov. 4/1 All of a sudden she (the mare, I suppose he meant) snarked an' begun to turn round.
2. intr. and trans. To find fault (with), to nag.
1882 Jamieson's Sc. Dict. IV. 314/2 To Snark,..to fret, grumble, or find fault with one. 1904 E. NESBIT Phœnix & Carpet x. 185 He remembered how Anthea had refrained from snarking him about tearing the carpet.
Altho both snarks might be "of imitative origin", another possible etymology of snark2 is from an alternation of nark "to annoy; to complain".
So we have two snarks: one older and perhaps dialectal, and one newer and in common use (it was used by Nesbit). I tend to think that snark2 formed the phonological inspiration for Carroll's Snark.